Recently, various preclinical and clinical studies on stem cell therapies have been conducted for various diseases such as cerebral infarction, traumatic neuronal injury, musculoskeletal disease, etc. However, the current technology has reached up to the level of simple extraction, culture and proliferation of stem cells and injection of the stem cells. Moreover, it is known, as a result of clinical studies up to now, that stem cell therapies have not yet shown a significant effect. Extensive research on a variety of genetically modified stem cells to promote the effect has continued to progress, but cell therapies using genes cannot be applied to the human body due to ethical issues.
Moreover, there are several problems in clinical application of the use of stem cells. Firstly, in the case of cell therapy products, there is a risk of tumor formation after stem cells are transplanted into tissue. Secondly, stem cells may cause arterial occlusion due to a relatively large size, resulting in cerebral infarction. Thirdly, stem cells can migrate to the brain during the acute phase when the brain-blood barrier is open but have limitations in crossing the brain-blood barrier due to a large size during the chronic stage. Lastly, inducing stem cells to specialized cells having desired properties for cell therapy products has limitation.
Contrarily, cell therapy using microvesicles has recently attracted attention as a method that is differentiated from the cell therapy using stem cells. Typically, microvesicles are small vesicles of 0.1 to 1 μm diameter and refer to cell membrane microparticles circulating in the blood, such as endothelial cells, platelets, etc. It is known that stem cell-derived microvesicles contain proteins, receptors as well as nuclear components and thus have a role in cell-to-cell communication. Moreover, the microvesicles contain a relatively small amount of animal serum compared to stem cells, and the risk of zoonosis can also be eliminated. In view of these characteristics of microvesicles, the cell therapy using microvesicles is expected to be a new paradigm that can overcome the limitations of existing stem cell therapies.
Therefore, extensive research aimed at using these stem cell-derived microvesicles instead of stem cells has continued to progress. For example, International Patent Publication No. WO 2010/070141 discloses a method for producing stem cell-derived microvesicles and therapeutic effects of the produced microvesicles on immune disease, allergic response, inflammatory disease, etc., and Korean Patent Publication No. 2010-122087 discloses a particle secreted by a mesenchymal stem cell and comprising at least one biological property of a mesenchymal stem cell and a technology using the particle as a therapeutic agent for cardioprotection.
However, there is not much research on stem cell-derived microvesicles, and it cannot be said that all stem cells that can be used for treatment of various diseases can be replaced by microvesicles. In particular, the correlation between microvesicles and neurogenesis has not been reported.
Therefore, if the generation of neuronal cells can be promoted using stem cell-derived microvesicles, it is possible to use them in the treatment of diseases related to neurological damage, and thus there is an urgent need to study the correlation between microvesicles and neuronal cells.